Slush pump



Patented July 21, 1942 UNITED STATES OFFICE SLUSH PUMP John Hart Wilson,Wichita-Falls, Tex.

Application July 10, 1939, Serial No. 283,652

4 Claims. (01.13826) The present invention relates to pumping mechanismsand particularly to pumps of the type employed in well drillingoperations for supplying mud or slush in the quantities and at thepressures necessary to facilitate such operations.

The modern well drilling mechanism is usually known'as a portabledrilling rig or rotary rig, and usually includes as one of itsoperatingunits a pump for withdrawing mud or slush from a slush pitorother storage reservoir and delivering itunder pressure to a conduit bymeans of which it is led to the drilling mechanism. It is generallypreferred to use for this purpose a pump of the crank and piston typehaving a plurality of cylinders into each of which the mud is drawn andfrom which itis immediately thereafter expelled. As is wellknown, therate of flow of fluid passing into the cylinder of a piston type pump'operated by a crank Varies throughout the suction stroke of the piston,varying closely as the sine of the crank angle. Likewise, in the casewhere two cylinders are employed and the cranks are disposed at rightangles, the flow of fluid into-either cylinder is greatest when thecrank has reached a position at right angles to the cylinder axis, andwith the crank in this position the flow of fluid into the othercylinder is theoretically zero. When the cranks are somewhat furtheradvanced, both cylinders will be drawing fluid at the same instant andwhen in one position the rate of flow of the fluid toward the cylinderswill be approximately 41% greater than it is when one piston is pumpingat its maximum rate and the other piston is pumping at its minimum rate,or zero.

In the event that there are four working cylinders and the pump is atwo-cylinder duplex pump, this variation inflow to the pump, or cycle,will repeat itself every 90 of crank angle movement. Hence it followsthatthere must be a very considerable'variation in the rate of flow ofthe stream offluid passing through the suction inlet aperture of thepump, and a corre-' sponding variation of flow in the slush intakeconduit leading to this port. Because of this, complications arise inthe pumping of mud or slush, which fluid is much heavier than water, andconsiderably more viscous, so that it is much more difiicult to quicklyaccelerate streams of such slush than streams of lighter and more freelyflowing fluids. As a result, a vacuum is frequently created'b'ehind thepiston" of a mud pump "moving on itssuotion stroke. An'y'such vacuummade'by a receding piston of'course re duces the eficieiicyof the pump;prevents it'from being operated at'as'highaspeed as desired, and alsocauses" ounding; the piston on its return stroke striking the solid bodyof "fluid with a considerable force, the poundingbeingsufiicient ifcontinued to actually wreck the pump.

It has heretofore been suggested that there may advantageously beemployed in connection with a multi cyliiider piston and crank type'ofslush pump a" device which may be designated a suction air"cha'mb'er,this'air chamber being connected toth'e'top of the suction lineand'actihg as a' storage reservoir for a relatively small quantityofslush which maybe drawn downwardly into the suction line when the pump'demand suddenly increases and which, theoretical 1y atle'ast, isagainrestored' to the'storage'chamher when the fluid flow to the pump isdeceleratin rather" than" accelerating." Naturally there should exist"in' the suction air chamber, above the level of the fluid therein; apartial vacuum, and'if this partial vacuum is notmaintained, the suctionair chamber becomes Wholly ineffective; In fact; unless the suctio'r'iair chamber'or auxiliary slush storage" chamber is maintained in properoperatingpondition', it'is'worse'than useless, sinceit may become simplya' reservoir for air which may be withdrawn into" the infiowing stream'of -slush inlar'ge sii'lglevolumes, causing loss of efi'iciency,pounding," and other undesirable effects. The mud or slush being pumpedusually contains aif'or other gas and some muds contain substantialquantities of gases. Con"- tinual leakage-of thesegas'e'sfrorri the mudp'assirg'to the pump intake, upwardly into the'aux'il iary chamber willdestroy th'ep'artial vacuum therein and thereby render the chamberuseless, since the only means for evacuating"the'air'from the chamber isthe' pump itself; and the pump is only effectivein accomplishingthis'when it' is initially operated and the passage between pump andchamber isas yet unobstructedbyinflowing slush.

It is the general purpose" of "the" present invention to provide meansin association with a slush or mud pump of the crank and pistontypewhich wil-l be'effective in smoothing'out the operation of the pumpand increasing its efiiciency', par ticularly at high speeds 'ofoperation. This is accomplishe'd' by" providing means for renderingefficien't the' heretofore" discredited suction air chamber; Such meansincludes automatically operating mechanis'm for maintaining a redetermined' degreeof sub-atmospheric pressure iii the top of the chamberandto therefore control the volume of mud or slush in the chamber withinclose limits. Preferably I position a vacuum pump closely adjacent theauxiliary chamber, and by a float controlled valve, bring the interiorof the upper end of the chamber into communication either with thispump, or with the atmosphere. Likewise, I connect the lower end of theauxiliary chamber to the pump intake line in a novel manner whicheliminates the possibility of air or gas passingupwardly into theauxiliary chamber from the inflowing stream of slush. As a result of theemployment of the invention a mud pump of given size may be used todeliver increased quantities of mud by being operated at higher speedsthan heretofore found 7 possible.

The improved mechanism is of very simple construction and may beembodied in various forms to suit special conditions. In theaccompanying drawing one form of the mechanism is illustrated by way ofexample but it will be appreciated by one skilled in the art that thecomponent elements of the invention may be varied in position and designwithout sacrifice of any of its advantageous results.

In the drawing:

Figure 1 shows, in side elevation, a slush pump of one type employed inoil field operations and likewise a mud or slush storage chamber of thetype contemplated by the present invention, this chamber being partiallybroken away;

Figure 2 is an axial vertical section through the lower portion of theauxiliary slush storage chamber and portion of the slush supply conduit,showing the port connecting conduit and chamber;

Figure 3 is a section on line 3,-3 of Figure 2; and

Figure 4 shows in side elevation a slush storage chamber to which hasbeen added means for automatically operating the valve which controlscommunication with a vacuum pump or the atmosphere.

The details of construction of the pump, which is indicated at P, arenot illustrated in the drawing since the pump may be of any suitabletype of crank and piston pump having the capacity required. The pumpshown may be driven from any convenient source of power, such as agasoline engine, and has an inlet port at a low level. The actual inletport of the pump is not shown but will be located at the end of the pipesection l0, which comprises one unit of the mud or slush conduit whichextends from the pump P to the slush pit. Iube or pipe I is shown insection in Figure 2 and it will be observed that it is provided withannular rings II and I2 by means of which one end of the tube may beattached to the frame of the pump and the other end to another pipesection such as indicated at I0. Encircling pipe section H] are theannular elements l3 and I4 the inner edge of each of which is welded tothe outer surface of the pipe. Encircling pipe I0 and having its endsengaging and welded to the annular elements I3 and I4, is a sleeve 15.Sleeve I5 has formed therein a relatively large aperture IS in its upperportion.

The storage chamber for mud or slush is indicated at H, this storagechamber being tubular and having its lower end attached as by welding tothe sleeve IS, the opening in its lower end being in register with theaperture l6 formed in the sleeve. The undersurface of the tube I0 is cutaway intermediate the annular rings I3 and M, to provide a port 3 whichbrings the interior of the tube I0 into communication with the interiorof the sleeve l5 and hence with the interior of the mud storage chamberH. To the upper end of the storage chamber I! there is connected a shorttube 20, this tube being in communication at its upper end with ahorizontally extending pipe 2| one end of which, indicated at 2|, beingconnected to a vacuum pump or to a chamber in which a sub-atmosphericpressure obtains, the other end, indicated at 2| being open to theatmosphere. A valve 22 controls communication between pipes 2| and 2|and valve 23 controls communication between the pipe 2| and the pipe 2 IBy manipulating the valves, the interior of the storage chamber may bebrought into communication either with the atmosphere or with the airexhausting means and hence the operator may establish within the chamberI! the exact degree of sub-atmospheric pressure which he desires.

A glass gauge is indicated at 25 by means of which the operator isenabled to ascertain the depth of the mud or slush within the storagechamber. Ordinarily the degree of subatmospheric pressure within thechamber will be so regulated with reference to the pump suction andother factors that the level of the upper surface of the slush withinthis chamber will be approximately that indicated in Figure l, the slushbeing drawn from the conduit It through the port I8 into the chamberdefined by the annular members I3 and I4 and the cylindrical member I5and thence upwardly into tubular chamber When the pump P is in operationand its pumping capacity varies in the manner previously described,slush will be drawn from the storage chamber when needed andsubsequently returned, thus smoothing out the inflow of liquid andmaking it unnecessary for the pump to accelerate the flow of the entirestream of slush back as far as the intake of conduit |3 at any time. Thestorage chamber will continue to function in this way indefinitely,although it may be necessary from time to time to manipulate the valve22 to connect the chamber H to the vacuum pump in order to maintain thepressure within chamber H at the desired point. However, increase inpressure in the chamber I! will occur only slowly since little, if any,air escapes into this chamber from the slush passing through the pipesection ID. This is because the air bubbles in the onflowing slush tendto gather at the top of the stream of slush and hence cannot escape intochamber because the communicating port I8 is .formed in the bottom ofthe pipe section I0.

In the form of the invention shown in Figure 4, the pressure within theslush storage chamber is automatically maintained at approximately apredetermined value by automatic means and hence the slush levelautomatically maintained at approximately the desired point. In thiscase it is preferred that a single valve 30 be employed which valve isof such type that it may be moved to bring the vertical conduit 3|, andhence the slush storage chamber 32, either into communication with pipeor duct 33 leading to the atmosphere or pipe or duct 34 leading to avacuum pump. The valve likewise has a third or intermediate position inwhich the pipe 3| is wholly closed so that the interior of the storagechamber 32 is out of communication with both the atmosphere and vacuumpump or the like.

Valve 33 is automatically actuated, the arm 35 fixed to the valve stembeing connected by means of a link 36 to one arm of a two-arm lever 31,the other arm of which is pivotally attached to the float 38 supportedby its own buoyancy upon the surface of the slush in a float chamber 39disposed laterally of the storage chamber 32. Lateral conduits 40 and 4|bring the interior of the float chamber 39 into communication with theinterior of the slush storage chamber 32 at vertically spaced points sothat the elevation of the upper surface of the body of slush in thefloat chamber 39 is always the same as that of the level of the surfaceof the body of slush within the storage chamber 32. Change of liquidlevel in the float chamber, therefore, results in either rising orfalling movement of the float and actution of the valve 30. The valve isthus automatically operated to bring the interior of storage chamber 32into communication with either the duct 33 or the duct 34 so that noattendant is needed to maintain the slush storage system operating withmaximum efficiency.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. The combination with a conduit through which slush or the like may bedrawn by suction, of a chamber for the storage of a quantity of slush tobe drawn downwardly into the conduit when the pressure in said conduitis suddenly decreased due to sudden increase in suction, said chamberbeing above the conduit, closed to the atmosphere, and communicatingwith the interior of the conduit only through an opening formed in theunderside of the conduit.

2. The combination with a conduit through which slush or the like may bedrawn by suction, of a chamber for the storage of a quantity of slush tobe drawn downwardly into the conduit when the pressure in said conduitis suddenly decreased due to sudden increase in suction, said chamberbeing above the conduit and communicating therewith only through anaperture formed in the underside of the conduit, and means formaintaining an approximately constant subatmospheric pressure withinsaid chamber above the level of the surface of the slush.

3. The combination with a conduit through which slush or the like may bedrawn by suction, of a chamber for the storage of a quantity of slush tobe drawn downwardly into the conduit when the pressure in said conduitis suddenly decreased due to sudden increase in suction, said chamberbeing above the conduit and means for maintaining an approximatelyconstant subatmospheric pressure within said chamber above the level ofthe surface of the slush, said means including a duct leading from thetop of said chamber, a vacuum pump to which said duct is connected, aduct leading from said chamber to the atmosphere, valve mechanismcontrolling both ducts, a float positioned to rise and fall with levelof the surface of the body of slush within the chamber, and meansoperatively connecting the float to the valve mechanism.

4. The combination with a conduit through which slush or the like may bedrawn by suction, of a chamber for the storage of a quantity of slush tobe drawn downwardly into the conduit when the pressure in said conduitis suddenly decreased due to sudden increase in suction, said chamberbeing above the conduit and closed to the atmosphere, a sleeveencircling said conduit and having a port therein to bring the interiorof the sleeve into communication with the interior of the chamber at thelower end thereof and closures for the ends of the sleeve, the conduithaving an aperture formed in its underside intermediate said closureswhereby the interior of the conduit is maintained at all times incommunication with the interiors of the sleeve and chamber.

JOHN HART WILSON.

